This invention relates generally to movable barrier operators and more particularly to obstacle detection.
Various kinds of movable barriers are known, including gates, doors, shutters and the like that move or pivot in horizontal or vertical directions to move between open and closed positions. Movable barrier operators of various kinds that effect motorized and controlled movement of such movable barriers are also known. Safety concerns exist with movable barrier operators. In particular, at least in some settings, care should be taken to ensure that a barrier that is moving to a closed position does not impact an obstacle and cause damage to either the obstacle or the barrier. The prior art proposes various solutions to address this issue.
Pursuant to one approach, an obstacle sensor attached to a leading edge of the movable barrier can detect an obstacle and provide a signal to the movable barrier operator to cause the operator to reverse movement of the barrier. Such sensors include switch style compressible strips having electrical conductors disposed therein that complete a circuit when the conductors are urged towards one another as the leading edge makes initial contact with an obstacle. Other sensors include pneumatic style sensors and light beam style sensors. Unfortunately, such sensors can themselves be damaged. When damaged, the sensor may no longer reliably detect an obstacle and thereby give rise to concerns regarding safe operation of the movable barrier.
The prior art suggests that an obstacle sensor can be tested from time to time to determine viability of the sensor. Towards this end, for example, a resistance can be added to a switch style compressible strip to facilitate detection of an open circuit that would indicate damage to the sensor. Unfortunately, such testing ability must ordinarily reside in proximity to the sensor itself and hence on the movable barrier itself. Wireless sensor interfaces are desired (to minimize the use of electrical supply and signaling cable on the door) but this typically requires the use of portable power supplies, such as batteries. To meet the limitations associated with such circumstances, prior art sensor interfaces only test sensor viability, if at all, infrequently (for example, once every ten minutes) or on an event-driven basis (for example, immediately following each closing of the door). Such infrequent or sporadic testing offers a considerable window of opportunity following damage to a sensor during which damage to the barrier or to an obstacle can occur.